Overactivation of poly(adenosine phosphate-ribose) polymerase 1 and molecular events in neuronal injury after deep hypothermic circulatory arrest: study in a rabbit model.

Objective: Although deep hypothermic circulatory arrest has been known to induce neuronal injury, the molecular mechanism of this damage has not been identified. We studied the key molecular mediators through cellular energy failure, excitotoxicity, and overactivation of poly(adenosine diphosphate-ribose) polymerase 1 in brain tissues of a rabbit model of deep hypothermic circulatory arrest similar to clinical settings.

Methods: We established 2 models of cardiopulmonary bypass (n = 15) and deep hypothermic circulatory arrest (n = 15) associated with cerebral microdialysis in rabbits. Deep hypothermic circulatory arrest lasted for 60 minutes. The measurements of glucose, lactate, pyruvate, and glutamate collected by means of microdialysis were quantified by using a microdialysis analyzer and high-performance liquid chromatography. The overactivation of poly(adenosine diphosphate-ribose) polymerase 1 was assessed by detecting immunostaining of poly(adenosine diphosphate-ribose). Histologic studies were used to identify neuronal morphologic changes and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling staining and poly(adenosine diphosphate-ribose) polymerase 1 Western blotting were used to identify apoptotic cells and early apoptotic signals.

Results: Deep hypothermic circulatory arrest significantly increased the lactate/pyruvate and lactate/glucose ratios and the glutamate value, whereas cardiopulmonary bypass did not (P < .05). Deep hypothermic circulatory arrest significantly increased the numbers of poly(adenosine diphosphate-ribose)-positive and apoptotic neurons compared with cardiopulmonary bypass (P < .05). The cleavage of poly(adenosine diphosphate-ribose) polymerase 1 was only found in the deep hypothermic circulatory arrest group. More injured neurons were found in the deep hypothermic circulatory arrest group (histologic scores, P < .05).

Conclusions: This study demonstrated that deep hypothermic circulatory arrest results in an overactivation of poly(adenosine diphosphate-ribose) polymerase 1, and that there were molecular events consisting of cellular energy failure, excitotoxicity, overactivation of poly(adenosine diphosphate-ribose) polymerase 1, and necrosis and/or apoptosis in neuronal injury.